Link issue

[Jan Beich]

Jason Bacon <bacon4000 at gmail.com> writes:

> BoltParams.o: In function
> `LMM::BoltParams::processCommandLineArgs(int, char**)':
> BoltParams.cpp:(.text+0x1a01): undefined reference to
> `boost::program_options::options_description::options_description(std::__cxx11::basic_string<char,
> std::char_traits<char>, std::allocator<char> > const&, unsigned int,
> unsigned int)'

Try replacing USE_GCC=yes with USES=compiler:gcc-c++11-lib to make the
port use GCC/libc++ rather than GCC/libstdc++.